This invention relates to an improved turn signal cancel mechanism for cancelling an actuated turn signal of a vehicle once the turn signal has been placed in one of two actuated positions by the vehicle operator.
As is well-known, a turn signal arm is used by a vehicle operator to actuate turn signals to signal a turn. When the turn is complete, the steering wheel is returned to its normal position and a turn signal cancel mechanism acts to return the turn signal arm back to its neutral or normal position, deactivating the turn signals. Additionally, the turn signal cancel mechanism must be able to hold the signal arm in the signalling position as the steering wheel is turned in the direction of the turn, this ability is referred to as bypass, and the turn signal mechanism must be able to yield if the turn signal arm is manually held in position and the steering wheel is turned in the cancel direction, that is opposite to the direction of the turn, so that the cancel mechanism is not damaged, this ability is referred to as jam cancel.
There are various types of signal cancel mechanisms that perform the above functions. Typically, they can be divided into two different groups, force cancel mechanisms and trip cancel mechanisms. The difference between these two types is the manner in which the restoring force is achieved to return the signal arm to the neutral position. Basically, force cancel mechanisms rely upon the geometry of the detent that holds the signal arm in place to restore the signal mechanism to the neutral position when the detent is forced from its holding position. Trip cancel mechanisms use stored energy from springs to restore the signal arm to the neutral position when the detent is tripped. Both of these cancel mechanisms have in the past typically used a single finger cancelling pawl. The pawl protrudes into the path of a cancelling member located on a vehicle's steering column. As the signaled turn is made, the cancel mechanism is in the bypass mode and when the turn is completed, the pawl is moved to cancel the turn signal and the turn signal arm returns to its neutral position with the pawl being retracted with respect to the steering column.
In an effort to more fully describe the operation of a typical cancel mechanism, a trip cancel mechanism will be described in more detail. It should be understood that this is merely one example of one type of cancel mechanism and particularly a type of trip cancel mechanism.
This example of a trip cancel mechanism includes a pivot assembly to which the signal arm is mounted. The pivot assembly includes a pair of restoring plungers to bias the pivot assembly to the normal position and a latching plunger which selectively latches the pivot mechanism in a desired signalling position. The latching is done by the interaction of the latching plunger with a latching or action form that has detents which are engaged by the latching plunger. The latching plunger is operatively connected to the single finger cancel pawl so that they can function responsively. For example, when the latching plunger is in a latched position, one end of the cancelling pawl can engage the plunger so that as the pawl is moved the latching plunger is moved from the detent.
The cancel pawl of this example is pivotally and reciprocally mounted in the cancel mechanism and has springs for urging the pawl outwardly and for aligning the pawl. A locating pin extends from the pawl and engages a locating ramp that is mounted to the end of the turn signal arm. The ramp is V-shaped with the apex being farther away from the steering column than the base of the V. The locating pin rides along the ramp in response to movement of the ramp by the turn signal arm. In the neutral position, the pin is at the apex of the V and the pawl is retracted with respect to the steering column. When a turn is signaled, the ramp moves and the pin rides along the ramp to the base of the V allowing the cancel pawl to extend out into the path of the cancelling member on the steering column. Simultaneously, the outer end of the latching plunger engages one of the detents in the latching form. The interaction between the latching plunger and the latching form is sufficient to overcome the biasing action of the restoring plungers so that the signal arm remains in the desired position.
At least one shoulder or a lobe of a cancelling member associated with the vehicle's steering column is adapted to come into contact with the finger of the cancel pawl. When the cancelling member rotates in a cancelling direction, the interaction of the finger with the cancelling member causes the cancel pawl to move and contact the latching plunger and trips it, dislodging it from the detent in the latching form. The biasing force of the restoring plungers returns the signal arm to the normal position and the finger is retracted within the turn signal cancel mechanism by movement of the ramp. When the cancelling member rotates in a non-cancelling direction, i.e., in the direction of the desired turn, the cancel pawl pivots slightly but does not trip the latching plunger, i.e., it is in the bypass mode.
One of the disadvantages of both types of turn signal cancel mechanisms is the amount of restoring force required to restore the turn signal arm to the neutral position. With reference to the trip mechanism just described, it requires sufficient spring force to be stored in the restoring plungers to pivot the signal arm back to neutral and to retract the cancel pawl against the bias of the springs attached to the cancelling pawl. With greater restoring forces there are numerous adverse effects, 1) there is more noise in the cancel mechanism when it is operated, 2) the tactiles of the system are adversely effected, 3) there is greater effort required to move the turn signal arm when making a turn, and 4) the system is restored to neutral at greater velocities which can result in damage to the system or a shortening of the mechanisms life. The same problems can occur in force cancel mechanisms due to the use of a single finger cancel pawl that is retracted into the cancel mechanism when the turn signal arm is in the neutral position.
The trip cancel unit described is also difficult to assemble. It can be difficult to properly locate the spring loaded cancel pawl with respect to the ramp in the mechanism. Further, there can be problems if the cancel pawl is not properly located with respect to the ramp or the springs do not properly bias the pawl which can result in the pawl not properly retracting creating noise problems and potential damage to the mechanism.